Build & Test Prep
Table of Contents
Team Vision for Build & Test Prep PhaseDuring this phase, the team planned to wrap up loose ends from the last phase of MSD I, including installing the new heaters, building a vent for the melter, finalize the 3D model and complete 2D drawings for the machine shop, select and order material for the mold as well as the door for the frame, and meet with Gary to discuss our designs.
We were able to complete most of the things we planned to for this phase. The installation of the new heaters has been delayed due to an issue with the timing of the order. We had planned to have ordered the heaters before winter break and received them by the start of the new semester, however the order was not processed until the start of the new semester so we are now waiting for the heaters to be shipped. We will continue to work on other subsystems while we wait for the heaters to arrive.
At the end of MSD I, the team was still working on some tasks that were not able to be completed by the end of the semester. During the first few weeks of MSD II we have been working to complete the leftover tasks. Before the winter break, we were able to secure an additional $350 from the MSD Office to add to our budget which allowed us to purchase the new heaters. The team also went back to the ER's and CR's to ensure all requirements were updated to meet the new HDPE material and the reduced 6"x 6" mold design.
- Order placed for new heaters
- 3D Model has been finalized
- Initial 2D Drawings have been completed
- Order placed for mold material
- We can begin machining process for the mold when the material is received
- Met with Gary from the machine shop
- Discussed cutting/rewelding parts of the frame
- Moving the metal bars to match the current locations in the 3D model
- Discussed electrical system
- Discussed cutting/rewelding parts of the frame
- New thermocouple works with old PID controller and can control it. Since it was not being controlled before, the heaters were ramping up to max temperatures and drawing max current likely causing the heaters to be damaged.
- Old PID controller switches too quickly causing
mechanical relay to constantly open and close, causing a
lot of noise and a lot of wear on the mechanical relay.
- Solution: remove mechanical relay, move to purely solid-state relay system. The SSRs we have can handle 240V AC and 25A each, and with six 500W heaters, the entire system will only theoretically draw 12.5A for the heaters.
- Old PID will be used for testing melting plastic while we work on programming the microcontroller. It will be used as a backup in case we run into issues with using the microcontroller. However, it only controls temperature based on one sensor which means it will not have the accuracy we need to prevent burning.
- New 500W heaters have been purchased. Old heaters are 300W each, so the whole system will increase from 1800W heat output to 3000W heat output. This should allow the system to reach desired temperatures faster and hopefully to reach the higher temperatures needed for PET if we are able to work with that later.
- We have been assessing where to place the IR temperature sensors to accurately measure temperature on the plate. We determined the field-of-view of the sensors (±45° from the center) from the datasheet to help us determine how far away the sensors can be placed and how much of the heated surfaces they will be reading from.
- Circuit-level schematic being designed in OrCAD currently so that we have documentation of how the whole system should be wired at each pin on each component. Currently we only have a high-level electrical system diagram which does not provide the wiring documentation needed for ourselves or for people in the future working on or maintaining the melter.
Insulation TestingAfter the mineral wool insulation was cut for each side of the frame and installed, the melter was ran with without any plastic chips and then with HDPE chips to test the performance of the insulation.
As seen previously in the Detailed Design Review, the melter was ran for 80 minutes and reaching only 195°C when the desired temperature range of 200-260°C. The second test involved testing the HDPE chips to verify the known melting temperature and capabilities. One side of insulation was removed every seven to eight minutes in order to continue compressing the mold as the chips melted. Running the melter for approximately 80 minutes resulted in temperatures comparable to the first test, considering the time insulation was removed to compress the mold. The test resulted in a thick sheet of melted HDPE that was difficult to remove from the mold, but verified the chips will melt in the current melter. The images below show the HDPE sheet that split into two halves. After the installment of the new heaters, the team will perform additional testing using McLube 860 mold release.
Current Models and Drawings
Below is a picture of the current melter device.
We will be removing some of the steel tubing and moving it to new locations for the new melter design. This will allow the team to reduce costs and wait time in purchasing new materials. Below is part of the drawing package that will be used to rebuild the melter frame.
The new melter, as shown below will compress up from a jack mounted on the bottom. A new jack support system with steel beams will be built and attached to one of the current mold plates, again repurposing parts of the current design to save money and resources. The new jack support is designed to keep the mold stable and aligned for uniform compression.
We also designed a new, smaller mold for testing the ability to melt plastic instead of focusing on a larger product. The new mold will produce a 6"x6" flat plastic sheet (HDPE). It is comprised of 3 separate sections that will come apart for easier removal of the plastic product from the mold. Alignment brackets will be welded to the bottom mold plate to align the mold sides and the top block will be set on top the plastic to be compressed when the jack is used.
Test PlanDuring this phase, the team revised the Test Plan Procedures adding specific details including:
- What are we going to test
- How are we going to perform the test
- Who is going to perform the test
- When is the test being performed
- Where is the test being performed
The purpose of the test procedures are to verify and record the performance of the melter to ensure all ER's are fulfilled. Important characteristics such as heating, production, equipment, product quality, compression, and safety will be tested.
- The initial Test Plan Procedures can be found here.
- The current Test Plan Template can be found here, but are being revised to match MSD's Test Plan Template
Test Plan Summary
A summary of the Test Plans can be found here. The document provides:
- CR's vs. ER's
- Working Test Plan Templates
The team will utilize this document heavily throughout the remainder of MSD II to test and record the data collected. The Team plans to have all remaining items ordered, all changes to the frame complete, and to collect all necessary tools and equipment for testing by the end of Phase 6.
Risk and Problem Tracking
At the end of MSD I, the team and customers changed the scope of the project from melting PET to melting HDPE due to the material properties. The team's request for additional funds was approved which allowed the team to order the new heaters. The size of the mold was also decreased to focus on proof of concept. The team's high risks from the previous phase are being resolved, but the team will continue to reevaluate risks throughout each phase.here
The team utilized a six step Problem Solving Process (PSP) to evaluate risks that have manifested into problems. This process will allow the team to identify problems and create a structured plan to resolve the issues.
The working Problem Tracking document can be found here